US4599898A - Method and apparatus for testing ball striking rackets - Google Patents

Method and apparatus for testing ball striking rackets Download PDF

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Publication number
US4599898A
US4599898A US06/657,008 US65700884A US4599898A US 4599898 A US4599898 A US 4599898A US 65700884 A US65700884 A US 65700884A US 4599898 A US4599898 A US 4599898A
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Prior art keywords
implement
mass
frequency
selected part
netting
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US06/657,008
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English (en)
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Walter Beer
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Assigned to BEERS AG. INGENIEURE A COMPANY OF SWITZERLAND reassignment BEERS AG. INGENIEURE A COMPANY OF SWITZERLAND ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: BEER, WALTER
Assigned to BEER, WALTER reassignment BEER, WALTER ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: BEERS AG INGENIEURE
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M5/00—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings
    • G01M5/0041—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings by determining deflection or stress
    • G01M5/005—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings by determining deflection or stress by means of external apparatus, e.g. test benches or portable test systems
    • A—HUMAN NECESSITIES
    • A63—SPORTS; GAMES; AMUSEMENTS
    • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
    • A63B60/00—Details or accessories of golf clubs, bats, rackets or the like
    • A63B60/42—Devices for measuring, verifying, correcting or customising the inherent characteristics of golf clubs, bats, rackets or the like, e.g. measuring the maximum torque a batting shaft can withstand
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L5/00—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes
    • G01L5/04—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes for measuring tension in flexible members, e.g. ropes, cables, wires, threads, belts or bands
    • G01L5/042—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes for measuring tension in flexible members, e.g. ropes, cables, wires, threads, belts or bands by measuring vibrational characteristics of the flexible member
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M5/00—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings
    • G01M5/0066—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings by exciting or detecting vibration or acceleration

Definitions

  • the present invention relates to improvements in a method and apparatus for ascertaining the quality of ball striking implements, such as tennis rackets, squash rackets and the like.
  • ball striking implements such as tennis rackets, squash rackets and the like.
  • the method and apparatus of the present invention can be used with equal advantage for ascertaining (i.e., testing) the quality of a wide variety of other types of ball striking implements and/or parts thereof.
  • the quality of tennis rackets is ascertained by subjecting them to a static test.
  • the racket is placed on a suitable support so that it is at a standstill, and a selected part of or the entire racket is thereupon subjected to the action of a force which tends to move the racket or a selected part thereof out of a position of rest.
  • the racket (or a selected part thereof) thereby undergoes an elastic (or even plastic) deformation.
  • the application of the force can entail a bending or flexing of the frame and/or a bending or flexing of the strings which constitute the netting of the racket.
  • the ratio P/x of the magnitude of the applied force (P) and the extent of the resulting deflection or deformation (x) of the frame and/or netting is presently considered to constitute a parameter which is indicative of the tension of the netting.
  • This parameter also called the spring constant
  • An object of the invention is to provide a novel and improved method of testing tennis rackets and/or analogous ball striking implements which avoids the drawbacks but exhibits all advantages of conventional testing methods.
  • Another object of the invention is to provide a novel and improved apparatus for testing ball striking implements.
  • a further object of the invention is to provide a method which renders it possible to accurately estimate the dynamic behavior of the implement in actual use.
  • An additional object of the invention is to provide a method which can be used for testing of selected parts of or entire ball striking implements with the same degree of facility and accuracy.
  • Still another object of the invention is to provide a method which can furnish short-lasting or more or less permanent indications of the results of the testing operation or operations.
  • a further object of the invention is to provide a method of the above outlined character which can be practiced by resorting to relatively simple, inexpensive and compact apparatus such as can be readily put to use not only in a plant but also on a tennis court, in the clubhouse or at another location close to the scene of play.
  • Another object of the invention is to provide a method which can be practiced by professionals or amateurs, which can be practiced with the desired degree of accuracy after a short period of demonstration or training, and which can be used for testing of a wide variety of ball striking implements.
  • One feature of the invention resides in the provision of a method of ascertaining the quality of ball striking implements, particularly (but not exclusively) tennis rackets and component parts thereof.
  • the method comprises the steps of imparting to a part of the implement (or to the entire implement) a vibratory movement at a selected (constant or variable) frequency for a selected interval of time, and monitoring during such interval that parameter or those parameters of the vibratory movement of the selected part of or the entire implement which is indicative of the quality of the selected part or the entire implement.
  • the vibratory movement imparting step can include periodically applying mechanical, acoustic or other energy impulses to the selected part of or to the entire implement.
  • the imparting step can include vibrating a selected part of the implement at a varying frequency and the monitoring step can include measuring the phase and recording a characteristic which is indicative of the measured phase.
  • a characteristic may constitute the slope of the curves denoting the phase subsequent to successive passages through zero.
  • the monitoring step (when the selected part is vibrated at a varying frequency) can include measuring the frequency of the selected part of the implement and recording (temporarily or permanently, e.g., by displaying the information or by storing the information on magnetic tape or the like) a characteristic which is indicative of the measured frequency.
  • the recording step can include recording the resonance frequency of the selected part of the implement and/or recording the width of the resonance frequency curve of the selected part of the implement.
  • the monitoring step can include ascertaining the velocity of propagation of vibratory disturbances in the selected part of the implement, while the selected frequency is constant.
  • the method can further comprise the step of attaching to the selected part of the implement a mass which is set in vibratory motion in the course of the vibration imparting step.
  • the monitoring step then preferably includes monitoring a parameter of the vibratory movement of such mass.
  • the apparatus comprises means for imparting to an implement or to a selected part of an implement a vibratory movement at a selected frequency for a selected interval of time, and means for monitoring (during such interval of time) that parameter of the vibratory movement of the selected part of or the entire implement which is indicative of its quality.
  • FIG. 1 is a partly sectional schematic and partly diagrammatic view of an apparatus which embodies one form of the invention and can be used for the practice of one embodiment of the improved method;
  • FIG. 2 is an amplitude-time diagram wherein the curve denotes the resonance frequency of the netting of a tennis racket;
  • FIG. 3 is a phase-frequency diagram wherein the curve indicates the phase and its slope at the zero point;
  • FIG. 4 is a view similar to that of FIG. 1 but showing a second apparatus wherein the energy which is applied to the selected part of an implement is in the form of sound waves;
  • FIG. 5 is a similar view of a third apparatus.
  • FIG. 6 is a diagram wherein the curves denote the signals which are evaluated by the apparatus of FIG. 5.
  • FIG. 1 shows an apparatus which can be used to test the quality of a ball striking implement in the form of a tennis racket 1.
  • the test involves a determination of the elastic behavior and/or damping characteristics of the implement 1.
  • the apparatus comprises a support 2 which is in engagement with the implement in the region of merger of the handle 1a into the frame 7 and a means 3 for imparting vibratory movements to a selected part of or to the entire implement.
  • the vibration imparting means 3 comprises an electric motor 4 whose output element carries a fixedly connected eccentric disc 5. The latter rotates in the complementary hole or socket of a pair of jaws 6 which grip the adjacent portion of the frame 7.
  • the reference character 8 denotes a variator or another suitable device which can vary the RPM of the motor 4 and hence the frequency of vibratory movement which is imparted to the frame 7.
  • the RPM of the motor 4 is monitored by a tachometer generator 9 or any other suitable frequency monitoring device whose output transmits corresponding signals to the respective input of a signal comparing stage 10.
  • a detector 11 is provided to ascertain the frequency and/or other characteristics of vibratory movements of the netting 1b of the implement 1.
  • the illustrated detector 11 can constitute a pickup head of the type used in apparatus for recording information on or for retrieving information from magnetic tapes or magnetic discs.
  • the detector 11 transmits signals which are indicative of the frequency and/or amplitude of vibratory movements of the netting 1b, and such signals are amplified by an amplifier 12 prior to transmission to the corresponding input of the signal comparing stage 10.
  • the variator 8 When the apparatus of FIG. 1 is in use, the variator 8 is actuated to vary the RPM of the motor 4 within a selected range and to thus vary the frequency of vibratory movements of the netting 1b.
  • the detector 11 detects vibratory movements of maximum amplitude (as at f o in the diagram of FIG. 2) when the RPM of the motor 4 matches or closely approximates the characteristic frequency of the netting 1b.
  • the output of the signal comparing stage 10 then transmits a signal to a digital display unit 13 which can be said to constitute a means for recording the information pertaining to that parameter of the netting 1b which is indicative of its quality, namely a quality which is important to the user of the implement 1 when the latter is in actual use.
  • the signal comparing stage 10 is designed to transmit a signal to the display unit 13 when the detector 11 ascertains the characteristic frequency f o of the netting 1b.
  • characteristic frequency is an indicator of the elastic behavior (and hence of the quality) of the netting 1b while the implement 1 is caused to strike a ball.
  • digital display unit 13 can be replaced with other information recording means, such as a printer, a stylus or the like, without departing from the spirit of the invention.
  • FIG. 1 An advantage of the apparatus which is shown in FIG. 1 is that it is surprisingly simple, compact, inexpensive and reliable. Moreover, the apparatus of FIG. 1 can be readily modified in a number of desirable ways, for example, in such a way that the signal comparing stage 10 transmits signals denoting the width 14 (note FIG. 2) of the amplitude of characteristic frequency f o of the netting 1b during the time interval which is selected by the person in charge of the test to actuate the variator 8, i.e., to change the RPM of the motor 4 within a selected range.
  • the width 14 of the curve denoting the resonance frequency of the netting 1b is indicative of the damping characteristics of the part 1b. Such damping characteristics constitute another parameter which is indicative of the quality of the tested part of the implement 1.
  • a mass 15 of predetermined weight which is separably attached to the netting 1b and whose vibratory movements are monitored by the detector 11.
  • the element 15 then constitutes the actual mass of the vibrating system.
  • the signal comparing stage (evaluating circuit) 10 in such a way that the digital unit 13 displays signals denoting the phase or the slope of the curve denoting the phase at the time when the mass 15 vibrates at the resonance frequency f o .
  • the phase at the zero point (see FIG. 3) is an indicator of the elastic behavior of the implement 1.
  • the slope of the curve denoting the phase at the zero point is indicative of the damping characteristics of the netting 1b (including friction at the points where the strings of the netting intersect each other).
  • FIG. 4 shows a modified apparatus wherein the means 3' for imparting vibratory movements to the netting 1b of the implement 1 is not in actual physical contact with the implement and the detector 11' is also out of contact with the netting and/or the mass 15 thereon.
  • the implement 1 is caused to rest on two supports 2 and 2' which engage the frame 7 at the locus of merger into the handle 1a and at a location which is disposed diametrically opposite the handle 1a.
  • the output element of the means 3' for imparting vibratory movements to the netting 1b is a loudspeaker 4' which is adjacent to but out of contact with the mass 15.
  • the latter is separably affixed to the central portion of the netting 1b.
  • the loudspeaker 4' emits acoustic signals which are caused to vibrate the mass 15 via disc 15a.
  • the means 3' further includes a generator which operates the loudspeaker 4', and the mass 15 is connected with a permanent magnet 16 constituting the core of an induction coil 11' which is the detector of the apparatus of FIG. 4.
  • the generator of the means 3' also transmits signals to the corresponding input of the signal comparing stage 10 another input of which receives signals from the induction coil 11' via amplifier 12.
  • the stage 10 of the apparatus which is shown in FIG.
  • the reference character 8' denotes a means for varying the excitation frequency of the generator in the means 3'.
  • the detector 11' transmits signals which are indicative of the amplitude of vibratory movements of the netting 1b (mass 15), and the signal which is displayed at 13 is indicative of a parameter that, in turn, denotes the quality of the netting 1b.
  • the mass 15, the permanent magnet core 16 thereon and the disc 15a constitute the actual vibrating mass of the implement 1 which is shown in FIG. 4.
  • the disc 15a can be said to constitute a means for receiving and transmitting forces generated by sound which is emitted by the loudspeaker 4'.
  • FIG. 5 shows an apparatus which constitutes a modification of the apparatus of FIG. 4 and wherein similar parts are denoted by reference characters corresponding to those employed in FIG. 4.
  • the only difference is that the detector 11' is attached to the netting 1b at a distance x from the mass 15 and loudspeaker 4'.
  • the loudspeaker 4' receives periodic signals from the generator of the vibratory movement imparting means 3', and such signals are transmitted to the disc 15a of the mass 15.
  • the detector 11' transmits signals to the corresponding input of the signal comparing stage 10 via amplifier 12.
  • the stage 10 ascertains the shift in the phase of signals which are received from the generator of the means 3' and amplifier 12.
  • the sequences of signals which the stage 10 of FIG. 5 receives from the generator of the means 3' and from the amplifier 12 is shown in FIG. 6.
  • the time differential ⁇ t between the two signals is indicative of the tension (hardness) of the netting 1b.
  • the improved apparatus can be modified in a number of additional ways without departing from the spirit of the invention.
  • the means for imparting vibratory movements can constitute any suitable mechanical, acoustic, electronic, electrodynamic, optical (between the ultraviolet and infrared ranges) or electromagnetic system.
  • the detector whose configuration and/or mode of operation will depend upon the characteristics of signals which are to be transmitted to the evaluating circuit 10 of the apparatus.
  • An important advantage of the improved method and apparatus is that, in contrast to the heretofore known static quality measurements, the ascertained parameter or parameters are much more accurately indicative of the behavior of the implement 1 in actual use.
  • Another important advantage of the improved method and apparatus is that they record signals which are obtained by averaging a large number of signals so that the displayed or otherwise recorded information is much more reliable and accurate than the one-shot measurements which are carried out in accordance with heretofore known proposals.
  • the signals which are furnished by the improved apparatus can denote the intervals of actual contact between the ball and the netting 1b when the implement 1 is in the process of striking the ball.
  • Deviations of the frequency or phase from certain values i.e., different resonance frequencies, different widths of the curves denoting the resonance frequency or different slopes of curves denoting the phase at the zero point, denote different periods of dwell of the ball in actual contact with the netting 1b. Deviations of such parameters from selected optimum values can denote that the implement 1 is less likely to propel the ball in a desired direction.
  • the improved method and apparatus is not subjected to stresses which could permanently affect its characteristics.
  • the frame 7 and/or the handle 1a of the implement 1 need not be subjected to bending or flexing stresses of a magnitude which could permanently affect the implement.
  • the improved method and apparatus can be used for determination of other parameters, such as the elasticity (kP) of the strings and others.
  • Still another important advantage of the improved method and apparatus is that the test can be completed within a fraction of the time which is required for static testing. This renders it possible to employ the improved apparatus in plants for mass production of ball striking implements to automatically test each of a short or long series of implements at the rate they are being produced. Moreover, the results of tests upon a short or long series of implements can be used to automatically or otherwise remedy the situation when the detected parameters indicate deviations of the quality from an optimum value.
  • the improved apparatus can be used with equal advantage by players and/or coaches and trainers on the court or in the clubhouse.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Aviation & Aerospace Engineering (AREA)
  • Health & Medical Sciences (AREA)
  • Biophysics (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Health & Medical Sciences (AREA)
  • Physical Education & Sports Medicine (AREA)
  • Measurement Of Mechanical Vibrations Or Ultrasonic Waves (AREA)
  • Force Measurement Appropriate To Specific Purposes (AREA)
  • Analysing Materials By The Use Of Radiation (AREA)
  • Investigating Strength Of Materials By Application Of Mechanical Stress (AREA)
US06/657,008 1983-10-12 1984-10-02 Method and apparatus for testing ball striking rackets Expired - Lifetime US4599898A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CH5545/83A CH662886A5 (de) 1983-10-12 1983-10-12 Verfahren zum bestimmen der qualitaet von ballschlaegern.
CH5545/83 1983-10-12

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US4599898A true US4599898A (en) 1986-07-15

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US06/657,008 Expired - Lifetime US4599898A (en) 1983-10-12 1984-10-02 Method and apparatus for testing ball striking rackets

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US (1) US4599898A (de)
EP (1) EP0141976B1 (de)
JP (1) JPS6098330A (de)
AT (1) ATE32380T1 (de)
CH (1) CH662886A5 (de)
DE (1) DE3469223D1 (de)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4870868A (en) * 1988-04-27 1989-10-03 Pennwalt Corporation Vibration sensing apparatus
US5060524A (en) * 1990-04-11 1991-10-29 Makser, S.A. Racket stringing tension measuring device
US5796005A (en) * 1991-06-12 1998-08-18 Frolow; Jack L. Flex meter for sports game implements
US6132326A (en) * 1997-09-23 2000-10-17 Jay Schweid, Inc. Sports implement customizing system
US6880403B1 (en) * 2000-08-28 2005-04-19 Mitsubishi Denki Kabushiki Kaisha Structure inspection device

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS62222612A (ja) * 1986-03-25 1987-09-30 Mitsubishi Electric Corp 電気機器の振動特性簡易測定方法
DE3736219C2 (de) * 1987-10-26 1994-08-18 Mauve Karl Eberhard Dr Verfahren und Vorrichtung zur Messung der Saitenspannung eines saitenbespannten Schlägers
US5163681A (en) * 1991-05-02 1992-11-17 George Hodgetts Golf club matching
CN109489921A (zh) * 2018-07-02 2019-03-19 马鞍山清净环保科技有限公司 一种用于多功能球拍测试仪的拍头控制装置及其使用方法

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3345862A (en) * 1964-01-21 1967-10-10 Robert G Rowe Resonance vibration apparatus for testing articles
US3345861A (en) * 1967-02-24 1967-10-10 Charles A Heath Acoustical testing method and apparatus
US4077256A (en) * 1977-01-10 1978-03-07 Bruce Lee Hollander Stringed racket face tension measuring device
US4109520A (en) * 1976-03-30 1978-08-29 Svenska Traforskningsinstitutet Method and means for measuring web tension in paper or foils
US4158962A (en) * 1978-03-03 1979-06-26 Paul Conoval Cable tension measuring apparatus

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4055999A (en) * 1976-12-23 1977-11-01 Cope James R Tension tester for tennis racket strings

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3345862A (en) * 1964-01-21 1967-10-10 Robert G Rowe Resonance vibration apparatus for testing articles
US3345861A (en) * 1967-02-24 1967-10-10 Charles A Heath Acoustical testing method and apparatus
US4109520A (en) * 1976-03-30 1978-08-29 Svenska Traforskningsinstitutet Method and means for measuring web tension in paper or foils
US4077256A (en) * 1977-01-10 1978-03-07 Bruce Lee Hollander Stringed racket face tension measuring device
US4158962A (en) * 1978-03-03 1979-06-26 Paul Conoval Cable tension measuring apparatus

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4870868A (en) * 1988-04-27 1989-10-03 Pennwalt Corporation Vibration sensing apparatus
US5060524A (en) * 1990-04-11 1991-10-29 Makser, S.A. Racket stringing tension measuring device
US5796005A (en) * 1991-06-12 1998-08-18 Frolow; Jack L. Flex meter for sports game implements
US6132326A (en) * 1997-09-23 2000-10-17 Jay Schweid, Inc. Sports implement customizing system
US6880403B1 (en) * 2000-08-28 2005-04-19 Mitsubishi Denki Kabushiki Kaisha Structure inspection device

Also Published As

Publication number Publication date
JPH0477865B2 (de) 1992-12-09
ATE32380T1 (de) 1988-02-15
DE3469223D1 (en) 1988-03-10
EP0141976B1 (de) 1988-02-03
CH662886A5 (de) 1987-10-30
EP0141976A1 (de) 1985-05-22
JPS6098330A (ja) 1985-06-01

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